In order to protect an occupant in the driver's seat or the passenger seat of a vehicle in a collision or an emergency, cars having an airbag device that has an inflatable and deployable airbag and is installed in, for example, the steering wheel or the instrument panel are widely used. Furthermore, in recent years, in order to further enhance the function of protecting an occupant, including an occupant seated in the rear seat, a side-surface airbag device that deploys an airbag in a curtain-like manner along an inner side wall window of the vehicle, between the window and the occupant, so as to cover the entirety thereof, is employed.
Meanwhile, there is conventionally known an airbag having a stitched portion (sewn portion), at which base fabrics are sewn together, in an air chamber formed between opposing base fabrics to restrict the shape of the deployed airbag to a flat shape (see PTL 1).
In this conventional airbag, the sewn portion is formed of a connecting portion having a line shape, which connects the base fabrics together, and circular protective connecting portions surrounding ends of the connecting portion to connect the base fabrics to each other. The protective connecting portions protect the ends of the connecting portion while reducing the concentration of force on the ends.
However, in this conventional airbag, because the sewing lines of these connecting portions intersect each other, when the stitches overlap each other during sewing, the previously sewn sewing thread may be cut. As a result, the strength of the intersection of the connecting portions against a force pulling the base fabrics apart from each other during inflation and deployment decreases. Furthermore, that force acts on the intersection (cut end) of the sewing threads, making the connecting portion likely to break from that portion, whereby part of the inflating and deploying airbag may be damaged.
Furthermore, this airbag has a problem in that, because the intersection of the sewing threads has low flexibility and, hence, the reaction force acting in the vicinity thereof when the airbag is folded is large, it is difficult to fold the airbag in a compact form precisely. In particular, in this airbag, the connecting portions are each formed of two sewing lines and are disposed close to each other, and the number of intersections is large. This partially further decreases the flexibility of the airbag, making it more difficult to fold the airbag. In addition, there is another problem in that the sewing is difficult because the ends of the connecting portion are folded back in the opposite direction and are double stitched for reinforcement, and because the ends of the protective connecting portions are sewn so as not to overlap but to be slightly shifted from each other.